When you fly across the country or halfway around the world, you might feel tired or out of sorts when you land. You also might have trouble sleeping at your usual time for the first few nights. These are symptoms of jetlag, a temporary sleep issue that occurs when your body’s internal clock (or circadian rhythm) is still in sync with the time at your original location rather than where you’ve traveled to.
Jetlag is common with air travel across multiple time zones. But did you know that you can experience this phenomenon without even leaving home? It’s true — and it’s called social jetlag.
Social jetlag causes the fatigue and fogginess we feel when social factors get in the way of our ideal sleep-wake cycle. Unbeknownst to many people, it can occur when there’s a conflict between what our bodies need, based on our internal biological clocks, and what our lives require in terms of our work, school, family, and social obligations. In other words, unlike the jetlag we get from traveling across time zones, social jetlag stems from how we move through our daily lives.
How is social jetlag calculated?
To put it more clearly, social jetlag is commonly defined as the difference between your weekday sleep schedule and your weekend sleep schedule.
To get a better sense of how the pandemic has affected social jetlag, we teamed up with SleepScore Labs, our partner in sleep data and science expertise, to look at more than 46,000 people’s sleep patterns from January 2019 to September 2021.
Sleep scientists typically define social jetlag as the difference between your midpoint sleep on weeknights versus your midpoint on weekends. (Think of midpoint sleep as the time on the clock when you’re halfway between falling asleep and waking up.) That’s how SleepScore Labs calculated social jetlag in its analysis.
The pandemic’s impact on social jetlag
According to SleepScore data, social jetlag decreased overall from 2019 to 2021, with some interesting generational variations:
- Baby Boomers (people ages 57 to 75) had the least social jetlag in all three years.
- Gen Xers (ages 41 to 56) had a slight uptick in social jetlag between 2020 and 2021, but they’re still less socially jetlagged than in 2019.
- Millennials (ages 25 to 40) had a more significant rebound in 2021, putting them closer to pre-pandemic social jetlag levels than they were in 2020.
- Generation Z (24 or younger) had the most social jetlag going into the pandemic. But even theirs reduced in 2020, and they sustained the decrease in 2021.
Interestingly, morning types were more likely to have negative social jetlag — meaning, earlier bedtimes and wake-up times on weekends than weekdays — while evening types had the biggest differences between their weekend and weekday sleep patterns.
Around the start of the March 2020 stay-at-home orders, sleep habits changed significantly, with all groups experiencing later bedtimes and wakeups. Gen Zers had the most dramatic shift, changing their wake-up time by nearly an hour, while other generations shifted theirs by about 30 minutes. In general, people from all generations moved their wake-up times more than their bedtimes, which means most people started getting more sleep.
“The COVID-19 pandemic has clearly impacted our work-life schedules, with more flexible schedules and autonomy in how and when we spend our time,” says Elie Gottlieb, Ph.D., applied sleep scientist at SleepScore Labs. “With this newfound flexibility and relaxed social pressures, people are sleeping longer and later on weekdays, which is appearing to improve the severity of social jetlag.”
The origins of social jetlag
German researchers coined the term “social jetlag” in 2006 while investigating how sleep schedules and quality vary between weekdays and the weekend. Since then, numerous studies have found that even if people get the same amount of sleep every night, the timing of that shut-eye matters. By putting people out of sync with their bodies’ circadian rhythms, sleep schedule shifts can have numerous health consequences.
Your circadian rhythms trigger various physical, mental, and behavioral changes across an approximately 24-hour cycle. Your exposure to light and dark conditions significantly impacts these rhythms. But so does your genetically determined chronotype — whether you’re an early bird or a night owl, for example.
These biological preferences occur against the backdrop of our basic sleep needs, which change with age. School-age kids typically need 9 to 12 hours of shut-eye per 24 hours, while teenagers thrive on 8 to 10 hours, and adults usually need 7 to 9 hours per night.
When analyzing the SleepScore data, “the most surprising finding was the sheer rate of widespread improvement in social jetlag across every chronotype and generation since the start of lockdowns,” Gottlieb says. Interestingly, there weren’t clear social jetlag differences between men and women or parents and non-parents, which surprised the researchers.
The consequences of social jetlag
Far more than just an annoyance or an inconvenience, social jetlag can have negative ripple effects on your body and mind. Research has found that adults with two or more hours of social jetlag have higher levels of the stress hormone cortisol and a higher resting heart rate than those with less than an hour of social jetlag. They were also less physically active.
Not surprisingly, living in a way that puts you perpetually out of sync with your natural sleep-wake rhythms has been linked with an increased risk for developing diabetes, weight gain, and metabolic syndrome (a cluster of conditions — such as elevated blood sugar, high blood pressure, low levels of HDL cholesterol, high triglyceride levels, and a large waist circumference — that can lead to heart disease and stroke). Researchers are also exploring possible links between social jetlag and certain cancers, including prostate cancer.
Meanwhile, some studies have found that social jetlag is associated with poorer subjective sleep quality. Social jetlag can alter resting brain activity in ways that can ramp up your appetite, leading to “hedonic feeding” (aka, eating just for the pleasure of it, not because you’re hungry). And a 2018 study found that people who typically sleep an hour and 45 minutes longer on the weekends than during the week have less healthy dietary patterns in general.
“If your sleep-wake rhythm is wacky through the week, this can affect your mood and cognition, compromising your ability to react quickly, think clearly, or be mentally sharp,” says Jade Wu, Ph.D., a psychologist and board-certified behavioral sleep medicine specialist based in Durham, North Carolina. Not surprisingly, greater social jetlag has been linked with an increased risk of depressive symptoms.
Reducing social jetlag
“The best way to recover from social jetlag is to start moving your schedule to something that’s more consistent and closer to the ideal,” says Dr. Chris Winter, neurologist, Sleep Advisor to Sleep.com, and author of "The Sleep Solution" and "The Rested Child." The brain thrives on consistent sleep, so you’ll want to find a routine that allows you to get the amount of nightly Zzz’s that you need.
Here are six ways to reduce social jetlag
- Stick with the same bedtime and awakening time. It’s best to maintain this consistency during the week and weekends as much as possible. When you can’t, it’s fine to build in an hour’s worth of wiggle room in either direction — but not more. The goal is to “try to get the same eight hours of sleep every day of the week,” Winter says.
- Reduce blue light in the evenings. Research has found that decreasing exposure to blue light in the evenings advances the release of melatonin (a hormone that promotes sleepiness) and sleep onset. You can reduce exposure to blue light by turning off digital devices — including computers, cell phones, tablets, and TVs — at least an hour before bedtime or by wearing blue-light-blocking glasses.
- Expose yourself to bright light. If you expose yourself to bright natural light first thing in the morning (by having breakfast by a sunny window, for example) and throughout the day, this will help promote healthy circadian rhythms and better sleep at night, Wu says.
- Give your kids a digital curfew. Have them turn off their digital devices, stop texting, and get off social media at least an hour before you want them to go to sleep, advises Wu. Research has found that increased screen time and texting at night are associated with — and therefore could be to blame for — social jetlag among teens.
- Let teens snooze on the weekends. Biologically speaking, teenagers are night owls, and they often stay up late doing homework during the week. And yet their school schedules require them to get up at 6 a.m. or 7 a.m. — before they’ve had enough sleep. “With teens, sleep deprivation is a bigger problem than social jetlag,” Wu says. She recommends that teens “sleep in on the weekends to recoup some of what they lost” during the week.
But that doesn’t mean letting them snooze until the afternoon, adds Winter. Encourage them to get up by 9 a.m. or 10 a.m., and if they’re still tired later in the day, let them take a nap in the afternoon, he recommends. - Advocate for more flexible schedules. “If workplaces could maintain some of the silver linings from the pandemic, allowing people more flexible work times, more remote work, and working with their natural chronotype, that would be great,” Wu says. Similarly, later starts to the school day, especially for teenagers, would allow them to live in better sync with their bodies’ natural sleep-wake cycles and regularly get the sleep they need, she says. Consider pushing for these changes in your workplace and community.
“While the improvements in social jetlag we’re seeing since 2019 are encouraging, they may be transient,” Gottlieb says. If or when we return to a pre-pandemic schedule that’s inflexible, requiring us to wake up and go to bed earlier than usual, social jetlag may make a comeback, he says. “It may be time to say goodbye to the traditional 9-to-5 workweek and think about a flex schedule with your chronotype in mind.”
Doing so could enhance not just your performance but your overall health and wellbeing.
